First Macro-Mesocellular Silica SBA-15-Si(HIPE) Monoliths

Subscriber access provided by Washington University | Libraries

Article

First Macro-Meso-cellular Silica SBA-15Si(HIPE) Monoliths :Conditions for Obtaining Self-Standing Materials Armand ROUCHER, Ahmed Bentaleb, Eric Laurichesse, Marie-Anne Dourges, Mélanie Emo, Véronique Schmitt, Jean-Luc Blin, and Rénal Backov Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.7b04483 • Publication Date (Web): 29 Dec 2017 Downloaded from http://pubs.acs.org on December 29, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Chemistry of Materials is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chemistry of Materials

First Macro-Meso-cellular Silica SBA-15-Si(HIPE) Monoliths: Conditions for Obtaining Self-Standing Materials

Armand Roucher,1 Ahmed Bentaleb,1 Eric Laurichesse,1 Marie-Anne Dourges,2 Mélanie Emo,3 Véronique Schmitt,1 Jean-Luc Blin3,* and Rénal Backov1,#* 1

CNRS, Univ. Bordeaux, CRPP, UPR8641, 115 Avenue Albert Schweitzer, 33600 Pessac, FRANCE. * E-mail: [email protected]

2

University of Bordeaux, Institute of Molecular Sciences, UMR 5255 CNRS, F-33400 Talence, France 3

Institut Jean Barriol, UMR CNRS 7565 SRSMC, Université de Lorraine, Faculté des sciences et technologies, BP 70239, 54506 Vandoeuvre lès Nancy cedex, FRANCE. * E-mail: [email protected] #

Present address: Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, office 1-382, Department of Civil and Environmental Engineering, Cambridge, MA02139, USA. E-mail: [email protected]

1 ACS Paragon Plus Environment

Chemistry of Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 35

Abstract Combining the emulsion and the cooperative templating mechanisms, self-standing macro-mesoporous SBA-15-Si(HIPE) monoliths (90-95% of porosity) have been synthesized for the first time. Materials have been prepared from the Pluronic (P123)/dodecane/water system in the presence of salt and TEOS as silica scaffold precursor. As increasing the ionic strength was shown to be ineffective toward obtaining self-standing monoliths, we induced a kosmotrope “order maker” effect within the starting silica gel making the use of (NH4)2SO4 salt to enhance silica polycondensation. Beyond its effect over the silica polycondensation, we show that the (NH4)2SO4 kosmotrope character has also a strong impact over the micelles organization at the mesoscale, with an input over the voids diameter and connections at the macroscopic length scale. The obtained SBA-15xSi(HIPE) self-standing foams exhibit thereby highly ordered mesopores, high specific surface area, tunable open macroporosity while offering mechanical strength (Young's modulus) of 0.15-1 MPa without collapsing at high strain.


Page 3 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Ordered mesoporous silicates1,2 have generated fascination in materials science and heterogeneous catalysis, as witness by thousands of publications in this domain.3 These mesoporous materials were stated as outstanding candidates for extending heterogeneous catalysis or adsorbents toward domains where pore sizes larger than those of zeolites were expected. Among the synthesized materials the most renown are certainly MCM-41 (Mobil Crystalline Materials) 4 using cetyltrimethylammonium as templating agent, SBA-15 (Santa Barbara Amorphous)5 using triblock copolymer Pluronic 123 as meso-scale template, MSU (Michigan State University)6 obtained from non-ionic polyoxyethylene alkyl ethers and HMS (Hexagonal Molecular Sieves)7,8 where dodecylamine is employed as a mesoscale templating agent. Despite academic success, we must confess that few real applications, or even none, have been extended toward the high scale industrial production. The first reason is certainly the use of sacrificial expensive templating agents. The second penalty is a consequence of the high degree of mesopores monodisperse character leading to materials with a unique pore size: 4.0 nm, 9.0 nm, 2.5 nm and between 2.5 and 5.0 nm for MCM-41, SBA-15, HMS, MSU respectively. The third issue is the fact that those mesoporous materials are generally obtained as powders and not as a monolith. Even if obtained as monolith, the high surface area will hinder good diffusion and accessibility through the whole monolith core while not avoiding high pressure drops. Those drawbacks are certainly the reasons why materials bearing dual or hierarchical porosities have today attracting widespread interest for industrial applications.9 Indeed the intrinsic advantages of assembling hierarchical porosity in one single material rely on the fluid hydrodynamic behaviors occurring at various length scales, from which the IUPAC porous classification has been constructed. If dealing with a Newtonian fluid (viscosity remains constant whatever the applied shear) as a solvent, at the microscopic length scale (1.5-2 nm) the fluid behavior will be driven by diffusion where molecular reactivity



Page 4 of 35

occurs and convection is negligible. At the mesoscopic length scale (2-50 nm) the convection is not negligible anymore, thereby the fluid hydrodynamics is a low convective fluid in which molecules are diffusing, this hydrodynamic behavior is called dispersion. This is also one of the reasons why mesoporous materials were so important within the last twenty years, as offering both molecular reactivity and mass transport pseudo-optimized. At the macroscopic length scale (50 nm and above) the mass transport is driven by convection where diffusion becomes negligible (sometimes the term advection is also employed to signify that molecular diffusion is present, even if negligible).10 The goal is overall to obtain materials bearing opened and hierarchical porosities and as far as possible to obtain monolithic materials and not powders as it is almost always the case. The reason is that, when dealing with monolithbased heterogeneous catalysis where both surface area and mass transport are optimized, the catalyst and the catalyzed species do not have to be separated in a final step anymore. The drawback is that obtaining self-standing monolith and not only powders bearing hierarchical porosity is everything but an easy task to reach, in that vein we have to underline the Nakanishi and co-workers' highly efficient path to address monolith generation obtained by coupling sol-gel process, phase separation and swelling lyotrope mesophases.11 An alternative way of obtaining such materials is to employ both lyotropic mesophases to create porosity at the meso-scale and concentrated emulsions to induce open porosity at the macro-scale. Those materials where labeled poly-HIPE (polymerized High Internal Phase Emulsion) and discovered by the industry. Such materials were most often obtained from the polymerization of a reverse concentrated emulsion, the continuous phase being composed of the organic polymerizable species.12 Contrary to what is often admitted, the first inorganicHIPE has also been pioneered by the industry13. Eight years later Imhof and Pine14 published a paper exhibiting the advantage of working with monodisperse non aqueous emulsions. Since, our group has shown how the macroscopic voids can be tuned on demand either


Page 5 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


playing with the starting emulsion oil volume fraction, we labeled those materials Si(HIPE)15 for silicic HIPE or by playing with Pickering based-emulsions, we labeled those materials Si(PHIPE) (Pickering-based High Internal Phase Emulsion).16 The Si(HIPE) series can either be hybridized to generate Organo-Si(HIPE)17 series reaching applications in photonics,18 metallic19 or enzymatic20 heterogeneous catalysis or be employed as hard exo-template to generate Carbon(HIPE) with emphases toward hydrogen storage,21 energy storage22 or enzyme-based energy conversion.23 Up to now, the link between the monolithic Si(HIPE) and the SBA-15 mesoporous materials was missing. Here we bridge the competences of these two sets of materials while generating the first SBA-15-Si(HIPE) foams. The materials are thus bearing a monolithic character and open macro-porosity while offering at the mesoscale a highly ordered mesoporous network addressing high surface area.

Materials and methods High purity dodecane (≥ 99%), hydrochloric acid 37wt % (HCl) ,tetraethylorthosilicate (≥ 99%, TEOS), (NH4)2SO4 and the non-ionic surfactant triblock copolymer, EO20PO70EO20 Pluronic P123 were purchased from Sigma-Aldrich. All the chemicals were used as received without any further purification. Material synthesis: In a typical synthesis, varied amounts of (NH4)2SO4 (corresponding to 0.1, 0.5, 1.0 and 2.0 M with regard to the total final aqueous phase) were added to 3.20 g (3.17 cm3) of the aqueous solution of P123 (5 wt%) and were stirred to obtain a homogeneous solution. Then, 1.00 g (0.833 cm3) of 37 % HCl aq. and 1.00 g (1.06 cm3) of TEOS were added in the previous solution and stirred by hand in a mortar until the pre-hydrolysis was complete. The emulsion is generated within a mortar by the addition of 7 g (9.33 cm3) of dodecane drop by drop under manual stirring. The final disperse phase volume fraction is therefore equal to 64.8 vol%. The 5 ACS Paragon Plus Environment


Page 6 of 35

emulsion was then transferred into a Teflon autoclave for hydrothermal treatment at 100°C for 24h. The material was washed with ethanol under Soxhlet for 48 h and dried at room temperature for 3 days. Finally, the materials were thermally treated under atmospheric conditions as follow: a first temperature increase is applied at 2°C/min until 180°C with a 2h plateau followed by a second temperature ramp at 1°C/min to reach 350°C. Temperature was held for 2h, then, a final temperature ramp at 1°C/min is imposed to reach 650°C with a 6h plateau. The cooling process was uncontrolled and directed by the oven inertia. Final expected meso-macroporous materials are labeled hereafter SBA-15xSi(HIPE) where x referred to (NH4)2SO4 concentration (0.1; 0.5; 1 or 2 M). Images of the final materials are reported on Figure 1. Characterization: SBA-15Si(HIPE) materials: Scanning electron microscopy (SEM) observations were performed with an HITACHI TM-1000 apparatus operating at 15 kV. Intrusion/extrusion mercury porosimetry were measured with a Micromeritics Autopore IV 9500 porosimeter. The mesoporous structure was observed with transmission electron microscopy (TEM) HITACHI-H600 operating at 75 kV. The materials were crushed into powder, dispersed in ethanol and deposed over a formvar/carbon grid and left dry in air before observations. Nitrogen sorptions isotherms were measured by using a Micromeritics ASAP 2010 apparatus. Samples were outgassed at 200°C overnight and weighted before sorption experiments. The surface area was determined by applying the multipoint Brunauer-Emmett-Teller (BET) model to describe the adsorption isotherm. The mesopore and the pore size distribution were determined by the Barret-Joyner-Halenda (BJH) method.24 X-ray measurements were performed on a Bruker Nanostar with a Cu anode working at 40 kV/35 mA coupled to a Göbel mirror system producing a beam with a wavelength of 0.15418 nm or an energy of 8 KeV. A Small-Angle X-ray Scattering (SAXS) configuration (Sample-detector distance, D =


Page 7 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


105 cm) with transmission geometry was chosen providing access to wave vectors q in the 0.1–2.3 nm‐1 range. Images were collected on a Hi-Star detector from Bruker and spectra were integrated with the Bruker software. For the mechanical properties, we cut the monoliths in small cylinder slices. A DHR-2 rheometer from TA Instruments has been employed for compression test with a plate-plate geometry with a diameter of 40 mm. The compression is applied with a constant velocity of 5 µm.s-1. Micelles structure in presence of salt: SAXS experiments were performed on a SAXSess instrument (Anton Paar), using line-collimation system. This instrument is attached to a ID 3003 laboratory X-Ray generator (General Electric) equipped with a sealed X-Ray tube (PANalytical, λ Cu Kα = 0.1542 nm) operating at 40 kV and 50 mA. A multilayer mirror and a block collimator provide a monochromatic primary beam. A translucent beam stop allows the measurement of an attenuated primary beam at q=0. Samples were put in a Special glass capillary (WJM Glas) before being placed at 25°C inside an evacuated sample chamber and exposed to X-Ray beam for about 90 minutes. Scattering of X-Ray beam was registered by a CCD detector (Princeton Instruments, 2084 x 2084 pixels array with 24 x 24 µm² pixel size), placed at 309 mm distance from the sample. Using SAXSQuant software (Anton Paar), the 2D image was integrated into one-dimensional scattering intensities I(q) as a function of the magnitude of the scattering vector q = (4π/λ) sin(θ), where 2θ is the scattering angle. All data were calibrated by normalizing the attenuated primary beam, before being corrected for the background scattering from the cell and the solvent and for slit-smearing effects by a desmearing procedure from SAXSQuant software using Lake method. After correction, the obtained intensities were scaled into absolute units using water as a reference material.



Page 8 of 35

Results and discussion Kosmotrope-chaotrope balance over ionic strength input. The syntheses of both Si(HIPE) monoliths and SBA-15 powders are occurring under strong acidic conditions where the organic-inorganic skeleton growth is promoted through ionic interactions, with the difference that the former makes the use of tetradecyltrimethylammonium bromide cationic surfactant (TTAB) while the later employs a non-ionic triblock copolymer one. When we tried to simply transpose the SBA-15 synthesis toward the Si(HIPE) one, we did never obtain self-standing monolith materials but powdered ones. In the same trend, rather fragile monolithic silica foams bearing a cubic organization of the mesopores, obtained under alkaline condition with non-ionic surfactant have been proposed by Esquena et al.25 It was thought15 that the good resistance of monoliths obtained with the cationic TTAB arises because of two effects: i) it influences the ionic strength of the initial sol at the origin of the Si(HIPE) and ii) due to the ammonium head group, it promotes the organization of the hybrid organic-inorganic growing clusters. We thus first focused on the ionic strength alone and replaced the cationic surfactant by NH4Cl without success whatever the salt concentration showing that electrostatics is not relevant here. Indeed whatever the NH4Cl concentration, the Debye length, that is to say the range of electrostatic repulsion is always of the orders of 0.3 nm due to presence of electrolytes (pH is adjusted at about 0.05 with HCl, well below the isoelectric point of silica around 2.1).26 Apart from electrostatic screening, ions are known for their ability to provoke order (kosmotrope) or disorder (chaotrope) following their position in the Hofmeister anion series [CO32-> SO42-> S2O32-> H2PO4-> F-> Cl-> Br- ≈ NO3-> I-> SCN-.27 As electrostatics is not relevant, the inefficiency of Cl- to lead to the formation of monolith likely results from its position in the Hofmeister series. To check this hypothesis, we chose the sulfate anion to induce a kosmotrope effect within the starting silica gel.28-30 As evidenced in the Figure 1 (embedded figures), changing Cl- into SO42-anion, we have obtained self-standing monoliths 8 ACS Paragon Plus Environment

Page 9 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


showing the efficiency of the kosmotrop effect on the synthesis. Additionally, we wanted to determine the effect of the cation keeping the sulfate and replacing NH4+ by Na+. No monolith could be obtained with sodium sulfate showing that both the choice of the anion and the cation are of utmost importance. To go into a deeper understanding and determine if the ammonium cation is necessary, materials have been prepared in the same conditions with magnesium sulfate MgSO4, sodium sulfate Na2SO4 and tetramethylammonium sulfate (N(CH3)4)2SO4 (see Supporting Information S1). As it can be seen on the pictures, despite the presence of some blocks with MgSO4, a monolith could only be obtained with the alternate ammonium salt ((N(CH3)4)2SO4). This result shows that additionally to the importance of the anion, the choice of the cation is also a key parameter for the generation of a self-standing monolith. Therefore, it seems that the ammonium cation brings also cohesion to the material. Kosmotrope-chaotrope balance and salting out effect at the macroscopic length scale. Under such configuration (NH4)2SO4 appears as the candidate of choice to obtain monoliths (Fig. 1). Their mechanical strength is slightly lower (see below) than the Si(HIPE) ones where TTAB was employed as meso-structurating and emulsion stabilizing agent. Contrary to Esquena et al.25 we did not have to use a cold lyophilisation process to dry the sample in order to minimize the collapsing effect induced by the capillarity forces when drying. Beyond, the thermal treatment is not an issue anymore; on the contrary it sinters the foams rending them more mechanically robust. As a direct consequence, as we will see later in the text, those SBA15-Si(HIPE) foams can endure mercury imbibition at ease when addressing mercury porosimetry investigations. After identifying the salt nature impact, we assessed its concentration effect. Considering the SEM images of the Figure 1 we can first observe that the macroscopic cell diameters decrease from 100 µm to 25 µm while increasing the salt concentration from 0.1 M to 1.0 M. The initial emulsion drop size is of the order of 60 µm (Supporting Information S2). It is worth noticing that the emulsion by itself is quite unstable. 9 ACS Paragon Plus Environment


Page 10 of 35

However, as the polycondensation occurs quickly at the synthesis temperature (100°C), the emulsion has no time to phase separate. The size evolution with salt concentration and the fact that a powder is obtained at 0.1 M demonstrate that the kosmotrope effect over the silica polycondensation is not high enough to stop the emulsion droplets coalescence when (NH4)2SO4 is employed at 0.1 M. Then, considering the Figures 1 c-h, we can notice an increase of the macroscopic void diameters while increasing the salt concentration. This process can be explained by a "salting-out" effect. For emulsions stabilized by a non-ionic surfactant of the polyoxyethylene ether class, we must consider an entropic repulsive force, which originates from the hydrophilic chains in good solvent on close approach.31 The entropic repulsive force can be affected by salts through an effect on the concentration of surfactant at the oil/water interface, on the extension of the chains due to a modification of the solvent quality. As already mentioned above, SO42- is a kosmotrope solute "order maker", it decreases the capability of water to act as a solvent, through a "salting-out effect" with nonionic surfactant, where most salting-out electrolytes lower the cloud point of non-ionic surfactant in direct proportion to their molar concentration,32,33 with a direct impact over the non-ionic surfactant packing density at the oil/water interface of oil-in-water emulsions.34 In order to evidence this effect, we prepared materials at a higher pH to slow down the polycondensation. It can be seen in Supporting Information S3, that below the monolith, a precipitate has formed evidencing the loss of solubility of the P123 nonionic surfactant by addition of (NH4)2SO4. Moreover, a 5wt% of P123 solution at room temperature (temperature at which the emulsion is prepared) in pure water or in 0.1 M of (NH4)2SO4 remain completely transparent and homogeneous while a precipitate appears for brines at 0.5, 1 and 2 M. As just demonstrated, in the present case, the increase of the (NH4)2SO4 concentration, diminishes the solubility of the non-ionic surfactant and thus its amount available for covering the oil/water


Page 11 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


interfaces. This effect enhances the coalescence phenomenon increasing the oil droplet diameters (Fig. 1 d-h) and modifying the pore volume fraction (Table 1). Insert Figure 1 here For 0.5 M of salt, the salting-out effect induces a solvent expulsion leading to an increase of the pore fraction. For higher salt concentrations, the salting-out effect is more important and the amount of P123 remaining and acting as surfactant decreases so much that the emulsion stability is not high enough to keep the pore volume fraction constant (0.63 and 0.52 for 1 and 2 M respectively). As a direct consequence of this instability, the final silica foams microscopic morphology evolves with the salt concentration as evidenced in Figure 1. Indeed, the structure, of the SBA-150.5Si(HIPE) is that of a foam with interconnected cells with windows while the SBA-151.0Si(HIPE) and SBA-152.0Si(HIPE) looks like fingerprints of adjacent spherical drops. In the case of SBA-151.0Si(HIPE), on Figure 1f, the macrocellular walls are almost free of internal connecting windows (holes within the walls) with a continuous external path of void (called hereafter external windows) created through the juxtaposition of adjacent cells, while SBA-152.0Si(HIPE) exhibits both internal and external windows (Fig. 1h). This latter morphology has also been observed within the Si(HIPE) series.15 When considering the Figure 1h we can see that the internal connecting windows are obvious, this characteristic witnesses the fact that when increasing the salt concentration from 1 M to 2 M respectively for the materials SBA-151.0Si(HIPE) and SBA-152.0Si(HIPE), the coalescence phenomenon is further expressed. Indeed, the patch size df between drops is proportional to the drop size at fixed dispersed phase volume fraction.35 Beyond SEM qualitative investigations we have also performed quantitative investigations through mercury porosimetry experiments. The first important result, as said before, is that these foams can support mercury infiltration being a sign of their good mechanical properties. When employing mercury porosimetry we have assessed the diameters of the voids that limit the 11 ACS Paragon Plus Environment


Page 12 of 35

mercury infiltration, in the present case it corresponds to the diameters of the connecting windows or the interstices between adjacent cells and not the cells themselves. The pore sizes distributions are shown within the Figure 2. Considering the pore sizes distribution, we can notice that they are spread and certainly multimodal. Despite this multimodal character two main pore sizes distribution are emerging at 120 µm and 20 µm for the foam SBA150.1Si(HIPE) and 68 µm and 4 µm for the foam SBA-150.5Si(HIPE). It is worth reminding that the initial emulsion drops size distribution was centered around 60 µm. This confirms the better emulsion stability at 0.5 M compared to the other salt concentrations. Considering the materials obtained with the higher salt concentrations we can notice that the pore sizes distributions is sharper for SBA-151.0Si(HIPE), where a bimodal or trimodal characteristic is more expressed than for SBA-152.0Si(HIPE). Insert Figure 2 here For the SBA-151.0Si(HIPE) we can see that three main pore diameters are emerging at 28 µm, 52 µm and 95 µm, while for the SBA-152.0Si(HIPE) foam, the curve expressed a multimodal pore size distribution in a range from 15 µm to 100 µm. Indeed, the main difference between those last two foams is that the pore sizes distribution of the SBA151.0Si(HIPE) expresses the presence of both external and internal junction cell, as it was the case for the Si(HIPE) series,15 while for the foam SBA-152.0Si(HIPE) the pore sizes distribution relies only on the internal cell junctions as the external ones are absent (Fig. 1h). Information concerning the porosity percentage as well as bulk and skeleton densities are summarized within the Table 1. We can see that the porosity percentages fall within 90-95% which is higher than classical Si(HIPE). As a direct consequence the bulk densities are lower (0.04 to 0.06 g cm-3) for foams obtained with a salt concentration from 0.1 M to 1.0 M, while being in the same range 0.1 g cm-3 when a salt concentration of 2.0 M is employed to generate the silica foams. The same trend is observed when dealing with the skeleton densities that are 12 ACS Paragon Plus Environment

Page 13 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


lower (below 1.0 g cm-3) compared to the traditional Si(HIPE) silica foams where the skeleton densities were higher (above 1.0 g cm-3).15 These evolutions where the bulk and skeleton densities are lowering when compared with Si(HIPE) is indeed expected. Kosmotrope-chaotrope balance and salting out effect at the mescoscopic length scale The Si(HIPE) are bearing a higher surface area (around 700-900 m2 g-1) but this high specific surface is essentially involved within the microporosity where the disorganized vermicular mesoporosity represents only 90 m2 g-1 at best.15 Here we can see that with the SBA-15Si(HIPE) series, the configuration is not the same where the mesoporosity is now reaching 50% of the total surface area (Table 1), that will induce lower bulk and skeleton densities measured by mercury porosimetry. Insert Table 1 here All the quantitative values that concern the mesoporosity proposed within the Table 1 have been obtained through nitrogen physisorption measurements depicted within the Figure 3. All the isotherms of the Figure 3 are class IV, when considering the IUPAC classification.36 We can see N2 adsorption at low relative pressure that reveals the presence of microporosity. Above the relative pressure of 0.4 we can observe the H1-type hysteresis loops between the adsorption and desorption curves, typical of mesoporous materials with homogeneous pore size.33 The pore sizes distributions have been calculated through the B.J.H.36 desorption curves. These pore sizes distributions (Figure 3 (inserts)) reveal rather well-defined profile of the mesoscopic voids centered at the values provided within the Table 1 (ranging between 5 nm-9 nm). The BJH surface areas providing the mesoscopic surface areas are provided within the table 1 with values ranging from 250 to 350 m2 g-1. Insert Figure 3 here



Page 14 of 35

Beyond nitrogen physisorption experiments, SAXS investigations are useful to assess the pores organization at the mesoscale with certainty (Figure 4). According to Figure 4, three more or less well-resolved reflection peaks can be observed on all samples in the range of 0.12 nm-1 of wave vectors. The peaks can be indexed to the (100), (110), and (200) reflection lines of a two-dimensional hexagonal p6mm symmetry, indicating a defined SBA-15 mesostructure.5 Insert Figure 4 here We can notice that all SAXS patterns exhibited the hexagonal 2D characteristic but for low salt concentration such as SBA-150.1Si(HIPE) and SBA-150.5Si(HIPE), the peaks (110) and (200) are barely distinguishable. Instead when we increased the salt concentration to 1M all three peaks can be discretized but at very high concentration like SBA-152.0Si(HIPE) even if they are still observed, the (110) and (200) reflection lines become less resolved and their intensity decreases, reflecting a less ordered channel arrangement. From the diffraction peaks it is possible to calculate the hexagonal-2D cell parameter "a" (a = 2d100/√3). Cell parameters of 11.2 nm, 11.9 nm, 11.2 nm and 9.5 nm are obtained for the foams SBA-150.1Si(HIPE), SBA-150.5-Si(HIPE), SBA-151.0Si(HIPE) and SBA-152.0Si(HIPE), respectively. If we consider the average mesoscopic void diameters proposed within the Table 1, then one can estimate the average silica wall thickness between the mesopores, the wall thickness will be equal to the cell parameter minus the mesopores diameters. As such, the determined silica wall thickness between the mesopores are around 4.0 nm, 5.6 nm, 2.2 nm and 4.5 nm for the foams SBA-150.1Si(HIPE), SBA150.5-Si(HIPE), SBA-151.0Si(HIPE) and SBA-152.0Si(HIPE), respectively. It is also possible to visualize the mesoscopic voids organization at the mesoscale with TEM, as depicted within the Figure 5. Insert Figure 5 here


Page 15 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


We have to underline the fact that TEM is a very local idea of the mesoscopic voids organization, contrary to SAXS experiments. Thereby we have performed screening of the materials with TEM and proposed images that reflect the materials organization. Overall the trend is in agreement with the SAXS experiment where the mesoscale organization is increased when increasing the salt concentrations from 0.1 M to 1 M, while increasing further the salt concentration promotes a decrease of the mesoscale organization, as it was the case with macroscopic voids trough the salting-out induced coalescence phenomenon. Indeed, at the mesoscale the salting out effect will be the same, it will minimize the non-ionic surfactant capabilities to be soluble in water. Under salt concentration increases from 0.1 M to 1.0 M the salting out effect will induce, through aggregation of the non-ionic surfactant, a higher compact configuration while reaching highly organized hexagonal-2D configuration of the lyotrope mesophases. This observation is in good accordance with the results reported by Dag et al.37 Indeed, in a paper dealing with the role of organic and inorganic additives on the properties of mesoporous silica particles prepared from the assembly of CTAB and P123, the authors have shown that the mesopore ordering is enhanced when the salt concentration is increased. In the absence of SO42-, only one reflection is detected on the XRD pattern, while the (110) and (200) reflections appear in the presence of sulfate anions at a concentration of 0.5 M. The resolution of the peaks also increases with the SO42- concentration. When increasing further the salt concentration to 2 M, some of the compacted non-ionic surfactant will precipitate through the strong salting-out effect and thereby will not contribute anymore to the lyotrope organization at the mesoscale enhancing thus the porosity disorder as witness both with SAXS (Fig 4) and TEM Fig (5g, h) experiments. This loss of the mesopore ordering can be also attributed to the shift of the lower consolute boundary (lcb) towards lower temperatures.34 Indeed in a paper dealing with the relation between the position of the lower consolute boundary of various nonionic surfactants in water and the structure of the



Page 16 of 35

mesoporous silica materials synthesized from these surfactants-based systems we have shown that the cooperative self-assembly mechanism is not favored if the lcb is not shifted toward high temperatures.38 Moreover, higher is the difference between the phase separation temperature and the temperature at which the silica precursor is added to the surfactant solution, better is the mesopore ordering.38

Kosmotrope-chaotrope balance and slating out effect over the P123 lyotropic mesophases. To investigate the effect of the presence of (NH4)2SO4 on the structure of the P123 micelles and therefore on the mesopore ordering SAXS measurements were also carried out on samples of Pluronic P123 at a concentration of 5 wt%, in water or in a (NH4)2SO4 solution at 0.1 M at 25°C. To perform this study, the obtained scattering data have been analyzed by the generalized indirect Fourier transformation (GIFT),39 taking into account the inter-particles interactions. The GIFT method allows determining the pair distance distribution function (PDDF), which corresponds to a histogram of the distances inside the particle. Figures 6a and 6b show the SAXS spectra represented in absolute units and the corresponding pair distance distribution functions (PDDF). Insert Figure 6 here

The curves presented in Figure 6b exhibit a bell-like shape characteristic of spherical particles. A supplementary information about the inhomogeneity of the particles (“core-shell” particles) is given by the small bump at around 5 nm (less pronounced for the sample without salt), as expected, given the electronic density difference between the EO-groups (ρEO = 371 e/nm3) and the PPO-chains (ρPO = 299 e/nm3). The maximum dimension of the particles can be estimated at around 20 nm. This value is in good agreement with the hydrodynamic diameter found with Dynamic Light Scattering (DLS) measurements (19 nm and 22.3 nm at 25°C, for the sample without and with salt, respectively). Considering that the length of the 16 ACS Paragon Plus Environment

Page 17 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


extended Pluronic P123 can be estimated at around 38.5 nm, the molecules are folded. The excess-electron density profiles can be obtained from the deconvolution of the pair-distance distribution function (Figure 6c). It confirms the “core-shell” type structure, as expected from the theoretical electronic density profiles (Figures 7b and 7c). The radius of the hydrophobic core can be defined where ∆ρ(r) changes of sign. Thus, the core radius can be evaluated at 3.9 nm for P123 in water and 4.4 nm for P123 in the (NH4)2SO4 solution. As the extended length of PPO-chains in the P123 molecules is about 24.5 nm, the PPO-units are bent and disordered in the core of the micelles, as represented in Figure 7a. Insert Figure 7 here

Moreover, the total radius is estimated at around 9.5 nm, which corresponds to the values obtained with the PDDF. Jansson et al.40 have investigated the structure of P123 micelles in water and they have obtained similar results than in this study. The PDDF displayed a distorted bell-shaped distribution, typical of spherical block copolymer micelles, with a maximum diameter of 20 nm. The excess electron density profile showed a typical core-shell structure with a radius of the PPO-rich core evaluated at 4.2 nm. Therefore, the addition of small amount of (NH4)2SO4 salt in the medium does not affect the structure of the micelles. However, it disturbs the cooperative templating mechanism, which is responsible of the formation of the hexagonal mesopore ordering of the macropores walls of the SBA15xSi(HIPE). In fact, the SAXS and TEM analyses of SBA-150.1Si(HIPE) reveal a less mesopore ordering than for SBA-15, i.e. for the materials prepared without salt. Increasing the (NH4)2SO4 content, larger aggregates are formed and they cannot be modeled and no information concerning the P123 aggregates can be obtained from SAXS. Nevertheless, we can assume that when preparing the SBA-15xSi(HIPE), the sulfate anions are localized closed the oxyethylene units and they make the P123 molecules more hydrophobic.41 The system behaves as if the number of PPO units increased. Therefore, the hydrophobic interactions are 17 ACS Paragon Plus Environment


Page 18 of 35

enhanced, resulting in a better mesopore ordering. Nevertheless, at concentration higher than 1M, the presence of SO42- shifts the lower consolute boundary curve of P123 towards lower temperature, which disturbed the cooperative templating mechanism and results in a less ordered mesopore arrangement. SBA-15Si(HIPE) Monolith mechanical properties. Finally, we have performed some preliminary mechanical tests over the SBA-15xSi(HIPE) materials (Figure 8). Insert Figure 8 here

From the figure 8 we can see classical mechanical compression curves bearing the elastic behavior at low strain (below 0.1) and the plastic domain at higher strain. The Young modulus calculated with the slope of the liner elastic domains are respectively 1 MPa for the classical Si(HIPE) obtained with TTAB as surfactant, 0.5 MPa and 0.15 MPa for the SBA150.5Si(HIPE) and SBA-151.0Si(HIPE) macrocellular monolithic foams. What is very interesting is to note that these mineralized foams do not collapse even after a strain of 40% and the overall behavior while increasing the strain is elastic at low strain, a pseudo-plastic domain at intermediary strain and compaction at high strain. We cannot explain yet this specific mechanical behavior and further mechanical studies are needed here. Also, The Si(HIPE) series is already offering advantageous “out of the box” catalytic properties42 and, in a near future, it would be very interesting to compare the SBA15-Si(HIPE) catalytic properties when functionalized with metallic nanoparticles or enzyme both with conventional Si(HIPE) and traditional mesoporous materials.43,44

Conclusion


Page 19 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For the first time, monolithic materials have been obtained exhibiting both the SBA-15 highly ordered mesoporosity and the macroporosity originating from the initial emulsion fingerprints. These materials have been synthesized by combining the sol-gel process, the elaboration of dodecane-in-water emulsions and the ternary phase behavior of Pluronic(P123)/dodecane/water in the presence of (NH4)2SO4. Indeed, we could combine the properties of both kinds of materials. We evidenced the importance of the salt chemical nature. We demonstrated through the use of (NH4)2SO4 that the ammonium gives cohesion to the material and is therefore necessary to obtain self-standing monolith, while SO42- triggers both the mesoscale organization and the morphology of the macroscopic voids due to its kosmotrope effect. The SBA-15Si(HIPE) series are highly porous (porosity between 90 and 95%) and exhibit lower bulk and skeleton densities than the conventional Si(HIPE) materials thanks to the enhanced mesoporosity. At the mesoscale, through a salting out effect of sulfate anions, the porosity can be tuned by varying the salt concentration. Results show that the salt plays a dual role. First, at the macroscale level it decreases the stability of the oilin-water emulsion, which involves an increase on the cell diameter with the salt concentration. Second, at the mesoscale level sulfate anions strengthen the hydrophobic interactions leading to a mesopore ordering. Nevertheless, at very high concentration, the kosmotrope effect of sulfate anions disturbs the cooperative templating mechanism and the SBA-15Si(HIPE) mesopororous network becomes less ordered. The SBA-15Si(HIPE) series have potential applications as heterogeneous catalysts as well as thermal and acoustic insulators.

Supporting Information: Materials monolith versus powdered states while varying the salt concentrations and salt effect on the starting emulsions.

Acknowledgements



Page 20 of 35

The work was financed by the ANR project n°ANR-15-CE07-0023: « Intensified & Sustainable Enzymatic Acylation Processes on Innovative Macroporous/Mesoporous Materials ». The authors would like to thank Professor Serge Ravaine for fruitful discussions.


Page 21 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References (1) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T.-W.; Olson, D. H.; Sheppard, E. W.; McCullen, S. B.; Higgins, J. B.; Schlenker, J. L., A New Family of Mesoporous Molecular Sieves Prepared with Liquid Crystal Templates. J. Am. Chem. Soc. 1992, 114, 10834-10843. (2) Di Renzo, F.; Cambon, H.; Dutartre, R., A 28-year-old Synthesis of Micelle-Templated Mesoporous Silica. Microporous Mater. 1997, 10, 283-286. (3) Taguchi, A.; Schüth, F., Ordered Mesoporous Materials in Catalysis. Micropor. Mesopor. Mat. 2005, 77, 1-45. (4) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S., Ordered Mesoporous Molecular Sieves Synthesized by a Liquid- Crystal Template Mechanism. Nature, 1992, 359, 710-712. (5) Zhao, D.; Feng, J.; Huo, Q.; Melosh, N.; Fredrickson, G. H.; Chmelka, B. F.; Stucky, G. D., Triblock Copolymer Syntheses of Mesoporous Silica with Periodic 50 to 300 Ångstrom Pores. Science, 1998, 279, 548-552. (6) Bagshaw, S.A.; Prouzet, E., Pinnavaia, T.J., Templating of Mesoporous Molecular Sieves by Non-ionic Polyethylene Oxide Surfactants. Science, 1995, 269, 1242-1244. (7) Tanev, P., T.; Pinnavaia, T. J., A Neutral Route to Mesoporous Molecular Sieves. Science, 1995, 267, 865-867. (8) Boissière, C.; Martines, M.A.U.; Tokumoto, M.; Larbot, A.; Prouzet E., Mechanisms of Pore Size Control in MSU-X Mesoporous Silica. Chem. Mater. 2003, 15, 509–515. (9) YAng, X.Y.; Léonard, Y.; Lemaire, A.; Tian, G.; Su, B.L. Self Formation Phenomenon to Hierarchically Structured Mesoporous Materials: Design, Synthesis, Formation Mechanism and Application. Chem. Commun. 2011, 47, 2763-2786. (10) Guyon, E.; Hulin, J. P.; Petit, L.; Mitescu, C. D. In Physical Hydrodynamics; Oxford University Press, 2001. (11) Amatani, T.; Nakanishi, K.; Hirao, K.; Kodaira, T. Monolithic Periodic Mesoporous Silica with Well-Defined Macropores. Chem. Mater. 2005, 17, 2114-2119. 21 ACS Paragon Plus Environment


Page 22 of 35

(12) Barby, D.; Haq. Z. Low Density Porous Cross-linked Polymeric Materials and Their Preparation and Use as Carriers for Included Liquid, European Patent 0060138, 1982. (13) Araya, A. Hydrophobic, Highly Porous, Three-Dimensional Inorganic Structures. US Patent 4888309, 1989. (14) Imhof, A.; Pine, D. Ordered Macroporous Materials by Emulsion Templating. Nature, 1997, 389, 948-951. (15) Carn, F.; Colin, A.; Achard, M. F.; Deleuze, H.; Sellier, E.; Birot, M.; Backov, R. Inorganic Monoliths Hierarchically Textured Via Concentrated Direct Emulsion and Micellar Templates. J. Mater. Chem. 2004, 14, 1370- 1376. (16) Destribats, M.; Faure, B.; Birot, M.; Babot, O.; Schmitt, V.; Backov R. Tailored Silica Macrocellular Foams: Combining Limited Coalescence-Based Pickering Emulsion and SolGel Process. Adv. Funct. Mat. 2012, 22, 2642-2654. (17) Ungureanu, S.; Birot, M.; Laurent, G.; Deleuze, H.; Babot, O.; Julían-López, B.; Achard, M. F.; Popa, M. I.; Sanchez, C.; Backov, R. One-Pot Syntheses of the First Series of Emulsion Based Hierarchical Hybrid Organic-Inorganic Open-Cell Monoliths Possessing Tunable Functionality (organo-Si(HIPE) series). Chem. Mater. 2007, 19, 5786-5796. (18) Brun, N.; Julian-Lopez, B.; Hesemann, P.; Guillaume, L.; Achard, M.-F.; Deleuze, H.: Sanchez, C.; Backov, R. Eu3+@Organo-Si(HIPE) Macro-Mesocellular Foams Generation: Synthesis, Characterization and Photonic Properties. Chem. Mater. 2008, 20, 7117-7129. (19) Ungureanu, S.; Birot, M.; Deleuze, H.; Babot, O.; Achard, M.-F.; Popa, M. I.; Sanchez, C.; Backov, R. Palladium Nanoparticles Heterogeneous Nucleation Within Organically Grafted Silica Foams and Their Use as Catalyst Supports Toward the Suzuki-Myaura and Mizoroki-Heck Coupling Reactions. Appl. Catal. A, 2010, 390, 51-58. (20) Brun, N.; Babeau-Garcia, A.; Achard, M. F.; Sanchez, C.; Durand, F.; Laurent, G.; Birot, M.; Deleuze, H.; Backov, R. Enzyme-Based Biohybrid Foams Designed for Continuous Flow Heterogeneous Catalysis and Biodiesel Production. Energy Environ. Sci. 2011, 4, 2840-2844. (21) Depardieu, M.; Janot, R.; Sanchez, C.; Deleuze, H.; Morcrette, M.; Gervais-Stary, C.; Backov, R. Nano-spots Induced Break of Boron Chemical Inertness A New Route Toward Reversible Hydrogen Storage Applications. J. Mat. Chem A, 2014, 2, 7694-7701. 22 ACS Paragon Plus Environment

Page 23 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(22) Depardieu, M.; Janot, R.; Sanchez, C.; Bentaleb, A.; Gervais-Stary, C.; Birot, M.; DemirCakan, R.; Morcrette, M.; Backov, R. Carbonaceous Multiscale-cellular Foams as Novel Electrodes for Stable Efficient Lithium- Sulfur Batteries. RSC Advances, 2014, 4, 2397123976. (23) Flexer, V.; Brun, N.; Courjean, O.; Backov, R.; Mano, N. Porous Mediator-Free Enzyme Carbonaceous Electrodes Obtained Through Integrative Chemistry for Biofuel Cells. Energy Environ. Sci. 2011, 4, 2097-2106. (24) Barret, E. P.; Joyner, L. G.; Halenda, P. P. The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computation from nitrogen isotherms. J. Am. Chem. Soc. 1951, 73, 373-380. (25) Nestor, J.; Vílchez, A.; Solans, C.; Esquena, J. Facile Synthesis of Meso/Macroporous Dual Materials with Ordered Mesopores Using Highly Concentrated Emulsion Based on a Cubic Liquid Crystal. Langmuir, 2013, 29, 432-440. (26) Brinker, C.J.; Scherer, G. W. Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing, Academic Press, 1990. (27) Hofmeister, F. Zur Lehre von der Wirkung der Salze. Arch. Exp. Pathol. Pharmacol. 1888, 24, 247-260. (28) Tobias, D. J.; Hemminger, J. C. Getting Specific About Specific Ion Effects, Science, 2008, 319, 1197-1198. (29) Zangi, R. Can Salting-in/Salting-out Ions Be Classified as Chaotropes/Kosmotropes? J. Phys. Chem. B, 2010, 114, 643-650 (30) Salis, A.; Ninham, B. W. Models and Mechanisms of Hofmeister Effects in Electrolyte Solutions, and Colloid and Protein Systems Revisited. Chem Soc Rev. 2014, 43, 7358-7377. (31) Helworthy P. H.; Florence, A. T. Rogers, J. A. Stabilization of Oil-in-Water Emulsions by Non-ionic Detergents. J. Colloid Interface Sci. 1971, 35, 23-33. (32) Schott, H. Effect of Inorganic Additives on Solutions of Non-ionic Surfactants. J. Colloid Interface Sci. 1997, 189, 117-122.



Page 24 of 35

(33) Bharatiya, B.; Ghosh, G.; Bahadur, P.; Mata, J. The Effects of Salts and Ionic Surfactants on the Micellar Structure of Tri-Block Copolymer PEO-PPO-PEO in Aqueous Solution. J. Dispersion Sci. Technol. 2008, 29, 696-701. (34) Florence, A. T.; Madsen, F.; Puisieux, F. Emulsion Stabilization by Non-ionic Surfactants: The Relevance of the Surfactant Cloud Point. J. Pharm. Pharmac., 1975, 27, 385-394. (35) G. Ceglia, L Mahéo, P. Viot, D. Bernard, A. Chirazi, I. Ly, O. Mondain-Monval and V. Schmitt. Formulation and mechanical properties of emulsion-based model polymer foams. Eur. Phys. J. E, 2012, 35, 1-11. (36) Sing, K. S.; Everett, D. H.; Haul, R. A.; Moscou, L.; Pierotti, R. A.; Rouquerol, J.; Siemieniewska, T. Reporting Physisorption Data for Gas/Solid Systems with Special Reference to the Determination of Surface Area and Porosity. Pure Appl. Chem., 1985, 57, 603-619. (37) Poyraz, A.S.; Dag, Ö. Role of Organic and Inorganic Additives on the Assembly of CTAB-P123 and the Morphology of Mesoporous Silica Particles. J. Phys. Chem. C. 2009, 113, 18596-18607. (38) Michaux, F; Blin, J.L.; Stébé, M.J. Relation between the Lower Consolute Boundary and the Structure of Mesoporous Silica Materials. Langmuir, 2008, 24, 1044-1052. (39) Glatter, O.; Kratky, O. in: Small Angle X-Ray Scattering, Academic Press, 1982, p.167. (40) Jansson, J.; Schillén, K.; Nilsson M.; Söderman O.; Fritz G., Bergmann A.; Glatter O. J. Small-Angle X-ray Scattering, Light Scattering, and NMR Study of PEO−PPO−PEO Triblock Copolymer/Cationic Surfactant Complexes in Aqueous Solution. Phys. Chem. B, 2005, 109, 7073-7083 (41) Poyraz, A.S.; Albayrak, C; Dag, Ö. The Effect of Cationic Surfactant and some Organic/Inorganic Additives on the Morphology of Mesostructured Silica Templated by Pluronics. Microporous Mesoporous Mater. 2008, 115, 548-555. (42) Roucher, A.; Depardieu, M.; Pekin, D.; Morvan, M.; Backov, R. Inorganic, Hybridized and Living Macrocellular Foams: "Out of the Box" Heterogeneous Catalysis. The Chemical Record 2017, DOI: 10.1002/xtcr.201700075. 24 ACS Paragon Plus Environment

Page 25 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(43) Wei, J.; Sun, Z.; Luo, W.; Li, Y.; Elzatahry, A. A.; Al-Enizi, A. M.; Deng, Y.; Zhao, D. New Insight into the Synthesis of Large-Pore Ordered Mesoporous Materials. J.A.C.S. 2017, 139, 1706-1713. (44) Jiang, Y.; Liu, S.; Zhang, Y.; Li, H.; He, H.; Dai, J.; Jiang, T.; Ji, W.; Geng, D.; Elzatahry, A. A.; Alghamdi, A.; Fu, D.; Deng, Y.; Zhao, D. Magnetic Mesoporous Nanospheres Anchored with LyP-1 as an Efficient Pancreatic Cancer Probe. Biomaterials 2017, 115, 9-18.



Page 26 of 35

TOC


Page 27 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figures and captions

Figure 1. Overall appearance of the as synthesized materials when varying the (NH4)2SO4 salt concentration. SEM visualization at different magnifications a-b) SBA-150.1Si(HIPE), c-d) SBA-150.5Si(HIPE), e-f) SBA-151.0Si(HIPE), g-h) SBA-152.0Si(HIPE). Inserts are optical images of the materials self-standing characteristics.



120 110 100 90

3

Log Differential Intrusion (cm /g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 35

80 70 60 50 40 30 20 10 0 0.1

1

10

100

Pore diameter (µm)

Figure 2. Pore sizes distributions obtained through mercury porosimetry. SBA-150.1Si(HIPE) (black curve), SBA-150.5-Si(HIPE) (red curve) (for the sake of clarity the curve has been translated 20 units up on the y axes), SBA-151.0Si(HIPE) (blue curve) (for the sake of clarity the curve has been translated 80 units up on the y axes) and SBA-152.0 Si(HIPE) (green curve) (for the sake of clarity the curve has been translated 100 units up on the y axes).


Page 29 of 35

600

400

300

200

100

0 0.0

0.2

0.4

2

1

0

0.6

5

10

15

0.8

1.0

400

300

200

100

20

Pore Diameter (nm)

Relative Pressure (p/p 0)

b) 500

dV/dlog(D) Pore Volume (cm³/gÅ)

Quantity Adsorbed (cm³/g STP)

a)

500


0 0.0

1.2

0.2

0.4

2

1

0

5

10

15

20

Pore Diameter (nm)

0.6

0.8

Relative pressure (p/p 0)

1.0

1.2

600

600

Quantity Adsorbed (cm³/g STP)

c) 500 400

dV/dlog(D) (cm³/gÅ)

300 200 100

3

2

1

0

0 0.0

0.2

0.4

0.6

0.8

5

Relative pressure (p/p 0)

10 15 20 Pore Diameter (nm)

1.0

500

d)

400 300


Quantity Adsorbed (cm 3/g STP)

600

Q uantity Adsorbed (cm 3 /g STP)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


200 100

25

1.2

0 0.0

0.2

0.4

0.6

1

0

5

10

15

0.8

Relative Pressure (p/p 0)

1.0

1.2

Figure 3. Nitrogen physisorption isotherms and pore size distribution (inset) for different SBA-15xSi(HIPE): a) SBA-150.1Si(HIPE), b) SBA-150.5Si(HIPE), c) SBA-151.0Si(HIPE) and d) SBA-152.0Si(HIPE). Black quares represent the adsorption curves and red circles the desorption curves.


20

Pore Diameter (nm)


(100)

Intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 35

d)

(110)

(200)

c)

b)

a)

0,5

1,0

1,5

2,0

-1

q (nm )

Figure 4. Evolution of the SAXS patterns with the variation of salt concentration: a) SBA150.1Si(HIPE), b) SBA-150.5-Si(HIPE), c) SBA-151.0Si(HIPE) and d) SBA-152.0Si(HIPE).


Page 31 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


a)

b)

c)

d)

e)

f)

g)

h)

Figure 5. TEM observations. a,b) SBA-150.1Si(HIPE), c,d) SBA-150.5-Si(HIPE), e,f) SBA151.0Si(HIPE) and g,h) SBA-152.0Si(HIPE).



Page 32 of 35

Figure 6. (a) SAXS spectra of P123 at a concentration of 5 wt. %, in water (purple) and in a (NH4)2SO4 solution (0.1 M) (green) at 25°C in log-log representation, (b) corresponding pair distance distribution and (c) corresponding excess-electron density profiles.


Page 33 of 35

a)

surfactant

b)

c)

380 360

ρ (e/nm )

3

340 320

340 320 300

300

micelle

380 360

3

ρ (e/nm )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


r

r

Figure 7. (a) Schematic representation of P123 micelles, (b) representation of the electronic densities of P123 in water, (c)representation of the electronic densities of P123 in a (NH4)2SO4 solution (0.1 M).



100

a)

b) 80

80 60

60

σ (kPa)

σ (kPa)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 35

40

20

20 0 0.0

40

0.1

0.2

0.3

0.4

0.00

0.02

0.04

0.06

0.08

0.10

Strain ε

strain ε

Figure 8. Normal stress σ vs strain ε during compression experiments. a) Red dots correspond to classic Si(HIPE) with TTAB used as a surfactant, blue dots for SBA-150.5Si(HIPE) and black dots SBA-151.0Si(HIPE). b) focus over on the linear domain (yellow background of a).


Page 35 of 35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table

Table 1. SBA-15xSi(HIPE) Porosity characteristics both at the macro- and mesoscopic length scales obtained respectively by mercury porosimetry and nitrogen physisorption measurements (grey background). BJH calculated from the nitrogen desorption curves.

x

Porosity (%)

Intrusion volume (cm3.g-1)

Bulk density (g.cm-3)

Skeletal density (g.cm-3)

BET surface area (m2.g-1)

Total pore volume (cm3.g-1)

BJH surface area (m2.g-1)

Average pore diameter (nm)

0.1

94

21.2

0.04

0.78

580

0.74

280

7.2

0.5

95

29.2

0.03

0.68

760

0.79

340

6.3

1

95

27.7

0.03

0.76

450

0.63

210

9

2

89

8.4

0.11

0.98

560

0.52

320

5


First Macro-Mesocellular Silica SBA-15-Si(HIPE) Monoliths

Recommend Documents